diff --git a/changelogs/unreleased/add_closed_at_attribute.yml b/changelogs/unreleased/add_closed_at_attribute.yml
new file mode 100644
index 00000000000..3afb75e8915
--- /dev/null
+++ b/changelogs/unreleased/add_closed_at_attribute.yml
@@ -0,0 +1,5 @@
+---
+title: Add 'closed_at' attribute to Issues API
+merge_request: 14316
+author: Vitaliy @blackst0ne Klachkov
+type: added
diff --git a/doc/api/issues.md b/doc/api/issues.md
index 8ca66049d31..cd2cfe8e430 100644
--- a/doc/api/issues.md
+++ b/doc/api/issues.md
@@ -95,6 +95,7 @@ Example response:
          "username" : "root"
       },
       "updated_at" : "2016-01-04T15:31:51.081Z",
+      "closed_at" : null,
       "id" : 76,
       "title" : "Consequatur vero maxime deserunt laboriosam est voluptas dolorem.",
       "created_at" : "2016-01-04T15:31:51.081Z",
@@ -205,6 +206,7 @@ Example response:
       "title" : "Ut commodi ullam eos dolores perferendis nihil sunt.",
       "updated_at" : "2016-01-04T15:31:46.176Z",
       "created_at" : "2016-01-04T15:31:46.176Z",
+      "closed_at" : null,
       "user_notes_count": 1,
       "due_date": null,
       "web_url": "http://example.com/example/example/issues/1",
@@ -311,6 +313,7 @@ Example response:
       "title" : "Ut commodi ullam eos dolores perferendis nihil sunt.",
       "updated_at" : "2016-01-04T15:31:46.176Z",
       "created_at" : "2016-01-04T15:31:46.176Z",
+      "closed_at" : "2016-01-05T15:31:46.176Z",
       "user_notes_count": 1,
       "due_date": "2016-07-22",
       "web_url": "http://example.com/example/example/issues/1",
@@ -358,7 +361,8 @@ Example response:
       "id" : 11,
       "title" : "v3.0",
       "created_at" : "2016-01-04T15:31:39.788Z",
-      "updated_at" : "2016-01-04T15:31:39.788Z"
+      "updated_at" : "2016-01-04T15:31:39.788Z",
+      "closed_at" : "2016-01-05T15:31:46.176Z"
    },
    "author" : {
       "state" : "active",
@@ -465,6 +469,7 @@ Example response:
    },
    "description" : null,
    "updated_at" : "2016-01-07T12:44:33.959Z",
+   "closed_at" : null,
    "milestone" : null,
    "subscribed" : true,
    "user_notes_count": 0,
@@ -533,6 +538,7 @@ Example response:
    "project_id" : 4,
    "description" : null,
    "updated_at" : "2016-01-07T12:55:16.213Z",
+   "closed_at" : "2016-01-08T12:55:16.213Z",
    "iid" : 15,
    "labels" : [
       "bug"
@@ -615,6 +621,7 @@ Example response:
   "state": "opened",
   "created_at": "2016-04-05T21:41:45.652Z",
   "updated_at": "2016-04-07T12:20:17.596Z",
+  "closed_at": null,
   "labels": [],
   "milestone": null,
   "assignees": [{
@@ -692,6 +699,7 @@ Example response:
   "state": "opened",
   "created_at": "2016-04-05T21:41:45.652Z",
   "updated_at": "2016-04-07T12:20:17.596Z",
+  "closed_at": null,
   "labels": [],
   "milestone": null,
   "assignees": [{
diff --git a/lib/api/entities.rb b/lib/api/entities.rb
index 52c49e5caa9..30b115b1b56 100644
--- a/lib/api/entities.rb
+++ b/lib/api/entities.rb
@@ -332,6 +332,7 @@ module API
     end
 
     class IssueBasic < ProjectEntity
+      expose :closed_at
       expose :labels do |issue, options|
         # Avoids an N+1 query since labels are preloaded
         issue.labels.map(&:title).sort
diff --git a/spec/fixtures/api/schemas/public_api/v4/issues.json b/spec/fixtures/api/schemas/public_api/v4/issues.json
index 8acd9488215..03c422ab023 100644
--- a/spec/fixtures/api/schemas/public_api/v4/issues.json
+++ b/spec/fixtures/api/schemas/public_api/v4/issues.json
@@ -9,6 +9,7 @@
       "title": { "type": "string" },
       "description": { "type": ["string", "null"] },
       "state": { "type": "string" },
+      "closed_at": { "type": "date" },
       "created_at": { "type": "date" },
       "updated_at": { "type": "date" },
       "labels": {
diff --git a/spec/requests/api/issues_spec.rb b/spec/requests/api/issues_spec.rb
index 1583d1c2435..972e57bc373 100644
--- a/spec/requests/api/issues_spec.rb
+++ b/spec/requests/api/issues_spec.rb
@@ -22,7 +22,8 @@ describe API::Issues, :mailer do
            state: :closed,
            milestone: milestone,
            created_at: generate(:past_time),
-           updated_at: 3.hours.ago
+           updated_at: 3.hours.ago,
+           closed_at: 1.hour.ago
   end
   let!(:confidential_issue) do
     create :issue,
@@ -738,6 +739,7 @@ describe API::Issues, :mailer do
       expect(json_response['title']).to eq(issue.title)
       expect(json_response['description']).to eq(issue.description)
       expect(json_response['state']).to eq(issue.state)
+      expect(json_response['closed_at']).to be_falsy
       expect(json_response['created_at']).to be_present
       expect(json_response['updated_at']).to be_present
       expect(json_response['labels']).to eq(issue.label_names)
@@ -748,6 +750,13 @@ describe API::Issues, :mailer do
       expect(json_response['confidential']).to be_falsy
     end
 
+    it "exposes the 'closed_at' attribute" do
+      get api("/projects/#{project.id}/issues/#{closed_issue.iid}", user)
+
+      expect(response).to have_http_status(200)
+      expect(json_response['closed_at']).to be_present
+    end
+
     context 'links exposure' do
       it 'exposes related resources full URIs' do
         get api("/projects/#{project.id}/issues/#{issue.iid}", user)